Two field experiments were carried out at the Farm of Environmental Studies and Research Institute, Sadat City University, during both seasons of 2013 and 2014to determine the effect of deficit of irrigation on vegetative growth characteristics, yield and its components and tubers quality on two potato cultivars Solanum tuberosum L.) cvs. Red Sun and Sophie) under sandy soil conditions. In this study, the experiment included 8 treatments, which were the combination between four levels of irrigations i.e., 100% (734.63 and 698.82 mm/fed.), 80% (587.7 and 559.1 mm/fed), 65% (477.6 and 454.23 mm/fed.) and 50% (367.32 and 349.41 mm/fed.) and two cultivars of potato (Red Sun, and Sophie) during both seasons 2013 and 2014 respectively. The results showed that, plant height, number of branches and fresh weight/plant, average tuber weight and tuber weight plant as well as tubers yield per feddan were significantly increased by using the highest level of irrigation ,while marketable yield % was not significantly affected and the size of tubers also was affected by irrigation levels . In addition, cv. Red Sun showed significant increasing in the vegetative growth expressed as plant height, fresh weight/plant, yield and its components and its quality compared with cv. Sophie. On the other hand cv. Sophie reflected significant increase in number of branches than cv. Red Sun. In this regard, marketable yield % was not significantly affected result of tested cultivars .The results showed that, the interaction between the cv. Red Sun and the highest level of irrigation resulted in significant increases in plant height, fresh weight/plant, average tuber weight and  tuber weight per plant as well as  tubers yield per feddan, marketable yield % and large tuber than  size more than 70 mm in diameter also results indicated that cv. Sophie with the highest level of irrigation significantly increased number of branches / plant than cv. Red Sun.